We are proposing a five-year, double-blind, placebo-controlled trial on the smoking cessation efficacy of bupropion as an adjunct to the standard combination of group cognitive-behavioral therapy (CBT) plus nicotine replacement. Our primary aims are 1) to examine the additional benefit of adding the antidepressant bupropion to a standard treatment for smoking cessation of CBT and nicotine replacement among smokers who have a history of either current or past unipolar depressive disorders (major depressive disorder, dysthymia, and minor depression), and 2) to determine, if bupropion indeed improves in this population a smoker's odds of quitting, whether its effect is achieved mainly through its impact on the negative mood states associated with depression. In order to provide a powerful test of both hypotheses, this study will enroll only smokers with a history of either current or past unipolar depressive disorders. In addition, allowing the inclusion of patients with a history of unipolar depressive disorders makes the proposed study more clinically relevant and its findings more generalizable, as several studies suggest that, as the prevalence of smoking continues to diminish in the general population, an increasing percentage of those who remain smokers are patients with psychiatric illnesses, especially depression. We expect that the efficacy of the standard combination of group CBT plus nicotine replacement will be greatly enhanced by the addition of bupropion in all smokers, but that the addition of bupropion will be especially helpful to those smokers who currently suffer from clinically significant depressive symptoms. The study involves the enrollment over 48 months of 300 individuals. We predict that 50 percent of the enrolled patients will meet criteria for current unipolar depressive disorders. After the 12-week acute treatment phase, patients will be followed for 12 months. The study design therefore involves the random assignment of current or past history of unipolar depressed patients to two treatment conditions: 1) group CBT plus nicotine patch plus bupropion (current depressive disorder bupropion group, estimated n=75; past depressive disorder bupropion group, estimated n=75); 2) group CBT plus nicotine patch plus placebo (current depressive disorder placebo group, estimated n=75; past depressive disorder placebo group, estimated n=75).